#!/usr/bin/env perl
use warnings;
use strict;

#
# Take a file of format (where [.] denote optional text)
# movie,user[,rating][,date]
# movie,user[,rating][,date]
# movie,user[,rating][,date]
# ...
#
# and produce an equivalent file of format
# movie:
# user[,rating][,date]
# user[,rating][,date]
# ...
# movie:
# user[,rating][,date]
# ...
#
# You can also use it in the inverse sense (movies for users).
#
my $movies = 0;
my $ratings = 0;
my $movie_id;
while (<STDIN>) {
  chomp;
  /^(\d+),?(.*)$/ or die "unexpected tuple line format ($_)";

  if (!defined($movie_id) || $movie_id != $1) {
    print "$1:\n";
    $movie_id = $1;
    $movies += 1;
  }
  $ratings += 1;
  print "$2\n";
}
print STDERR "Processed $ratings ratings of $movies movies (or users).\n";


# Copyright (c) 2009 John Lees-Miller
# 
# Permission is hereby granted, free of charge, to any person
# obtaining a copy of this software and associated documentation
# files (the "Software"), to deal in the Software without
# restriction, including without limitation the rights to use,
# copy, modify, merge, publish, distribute, sublicense, and/or sell
# copies of the Software, and to permit persons to whom the
# Software is furnished to do so, subject to the following
# conditions:
# 
# The above copyright notice and this permission notice shall be
# included in all copies or substantial portions of the Software.
# 
# THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
# EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES
# OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
# NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT
# HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY,
# WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
# FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR
# OTHER DEALINGS IN THE SOFTWARE.

